=head1 VERSION
-Version 0.03
+Version 0.06
=cut
our $VERSION;
BEGIN {
- $VERSION = '0.03';
+ $VERSION = '0.06';
}
=head1 SYNOPSIS
package X;
- use Scope::Upper qw/reap localize localize_elem localize_delete/;
+ use Scope::Upper qw/reap localize localize_elem localize_delete :words/;
sub desc { shift->{desc} }
my ($desc) = @_;
# First localize $x so that it gets destroyed last
- localize '$x' => bless({ desc => $desc }, __PACKAGE__) => 1;
+ localize '$x' => bless({ desc => $desc }, __PACKAGE__) => UP; # one scope up
reap sub {
my $pkg = caller;
my $x = do { no strict 'refs'; ${$pkg.'::x'} }; # Get the $x in the scope
print $x->desc . ": done\n";
- } => 1;
+ } => SCOPE 1; # same as UP here
localize_elem '%SIG', '__WARN__' => sub {
my $pkg = caller;
my $x = do { no strict 'refs'; ${$pkg.'::x'} }; # Get the $x in the scope
CORE::warn($x->desc . ': ' . join('', @_));
- } => 1;
+ } => UP CALLER 0; # same as UP here
- localize_delete '@ARGV', $#ARGV => 1; # delete last @ARGV element
+ # delete last @ARGV element
+ localize_delete '@ARGV', -1 => UP SUB HERE; # same as UP here
}
package Y;
...
} # "pie: done" is printed
+ package Z;
+
+ use Scope::Upper qw/unwind want_at :words/;
+
+ sub try (&) {
+ my @result = shift->();
+ my $cx = SUB UP SUB;
+ unwind +(want_at($cx) ? @result : scalar @result) => $cx;
+ }
+
+ ...
+
+ sub zap {
+ try {
+ return @things; # returns to try() and then outside zap()
+ }
+ }
+
+ my @what = zap(); # @what contains @things
+
=head1 DESCRIPTION
This module lets you defer actions that will take place when the control flow returns into an upper scope.
Currently, you can hook an upper scope end, or localize variables, array/hash values or deletions of elements in higher contexts.
+You can also return to an upper level and know which context was in use then.
=head1 FUNCTIONS
+In all those functions, C<$context> refers to the target scope.
+
+You have to use one or a combination of L</WORDS> to build the C<$context> to pass to these functions.
+This is needed in order to ensure that the module still works when your program is ran in the debugger.
+Don't try to use a raw value or things will get messy.
+
+The only thing you can assume is that it is an I<absolute> indicator of the frame.
+This means that you can safely store it at some point and use it when needed, and it will still denote the original scope.
+
=cut
BEGIN {
XSLoader::load(__PACKAGE__, $VERSION);
}
-=head2 C<reap $callback, $level>
+=head2 C<reap $callback, $context>
-Add a destructor that calls C<$callback> when the C<$level>-th upper scope ends, where C<0> corresponds to the current scope.
+Add a destructor that calls C<$callback> when the upper scope represented by C<$context> ends.
-=head2 C<localize $what, $value, $level>
+=head2 C<localize $what, $value, $context>
-A C<local> delayed to the time of first return into the C<$level>-th upper scope.
+A C<local> delayed to the time of first return into the upper scope denoted by C<$context>.
C<$what> can be :
=over 4
If the sigil is C<'$'>, L</localize> follows the same syntax as C<local $x = $value>, i.e. C<$value> isn't dereferenced.
For example,
- localize '$x', \'foo' => 0;
+ localize '$x', \'foo' => HERE;
will set C<$x> to a reference to the string C<'foo'>.
Other sigils (C<'@'>, C<'%'>, C<'&'> and C<'*'>) require C<$value> to be a reference of the corresponding type.
When the symbol is given by a string, it is resolved when the actual localization takes place and not when C<localize> is called.
This means that
- sub tag { localize '$x', $_[0] => 1; }
+ sub tag { localize '$x', $_[0] => UP }
will localize in the caller's namespace.
=back
-=head2 C<localize_elem $what, $key, $value, $level>
+=head2 C<localize_elem $what, $key, $value, $context>
Similar to L</localize> but for array and hash elements.
If C<$what> is a glob, the slot to fill is determined from which type of reference C<$value> is ; otherwise it's inferred from the sigil.
C<$key> is either an array index or a hash key, depending of which kind of variable you localize.
-=head2 C<localize_delete $what, $key, $level>
+=head2 C<localize_delete $what, $key, $context>
Similiar to L</localize>, but for deleting variables or array/hash elements.
C<$what> can be:
=back
-=head2 C<unwind @values, $level>
+=head2 C<unwind @values, $context>
+
+Returns C<@values> I<from> the context pointed by C<$context>, i.e. from the subroutine, eval or format just above C<$context>.
-Returns C<@values> I<from> the context indicated by C<$level>, i.e. from the subroutine, eval or format just above C<$level>.
-The upper level isn't coerced onto C<@values>, which is hence always evaluated in list context.
+The upper context isn't coerced onto C<@values>, which is hence always evaluated in list context.
+This means that
+
+ my $num = sub {
+ my @a = ('a' .. 'z');
+ unwind @a => HERE;
+ }->();
+
+will set C<$num> to C<'z'>.
+You can use L</want_at> to handle these cases.
+
+=head2 C<want_at $context>
+
+Like C<wantarray>, but for the subroutine/eval/format just above C<$context>.
+
+The previous example can then be "corrected" :
+
+ my $num = sub {
+ my @a = ('a' .. 'z');
+ unwind +(want_at(HERE) ? @a : scalar @a) => HERE;
+ }->();
+
+will righteously set C<$num> to C<26>.
=head1 WORDS
-=head2 C<TOP>
+=head2 Constants
-Returns the level that currently represents the highest scope.
+=head3 C<TOP>
-=head2 C<HERE>
+Returns the context that currently represents the highest scope.
-The current level - i.e. C<0>.
+=head3 C<HERE>
-=head2 C<UP $from>
+The context of the current scope.
-The level of the scope just above C<$from>.
+=head2 Getting a context from a context
-=head2 C<DOWN $from>
+For any of those functions, C<$from> is expected to be a context.
+When omitted, it defaults to the the current context.
-The level of the scope just below C<$from>.
+=head3 C<UP $from>
-=head2 C<SUB $from>
+The context of the scope just above C<$from>.
-The level of the closest subroutine context above C<$from>.
+=head3 C<SUB $from>
-=head2 C<EVAL $from>
+The context of the closest subroutine above C<$from>.
-The level of the closest eval context above C<$from>.
+=head3 C<EVAL $from>
-If C<$from> is omitted in any of those functions, the current level is used as the reference level.
+The context of the closest eval above C<$from>.
-=head2 C<CALLER $stack>
+=head2 Getting a context from a level
-The level corresponding to the stack referenced by C<caller $stack>.
+Here, C<$level> should denote a number of scopes above the current one.
+When omitted, it defaults to C<0> and those functions return the same context as L</HERE>.
+
+=head3 C<SCOPE $level>
+
+The C<$level>-th upper context, regardless of its type.
+
+=head3 C<CALLER $level>
+
+The context of the C<$level>-th upper subroutine/eval/format.
+It kind of corresponds to the context represented by C<caller $level>, but while e.g. C<caller 0> refers to the caller context, C<CALLER 0> will refer to the top scope in the current context.
=head1 EXPORT
-The functions L</reap>, L</localize>, L</localize_elem>, L</localize_delete> and L</unwind> are only exported on request, either individually or by the tags C<':funcs'> and C<':all'>.
+The functions L</reap>, L</localize>, L</localize_elem>, L</localize_delete>, L</unwind> and L</want_at> are only exported on request, either individually or by the tags C<':funcs'> and C<':all'>.
-Same goes for the words L</TOP>, L</HERE>, L</UP>, L</DOWN>, L</SUB>, L</EVAL> and L</CALLER> that are only exported on request, individually or by the tags C<':words'> and C<':all'>.
+Same goes for the words L</TOP>, L</HERE>, L</UP>, L</SUB>, L</EVAL>, L</SCOPE> and L</CALLER> that are only exported on request, individually or by the tags C<':words'> and C<':all'>.
=cut
our @EXPORT = ();
our %EXPORT_TAGS = (
- funcs => [ qw/reap localize localize_elem localize_delete unwind/ ],
- words => [ qw/TOP HERE UP DOWN SUB EVAL CALLER/ ],
+ funcs => [ qw/reap localize localize_elem localize_delete unwind want_at/ ],
+ words => [ qw/TOP HERE UP SUB EVAL SCOPE CALLER/ ],
);
our @EXPORT_OK = map { @$_ } values %EXPORT_TAGS;
$EXPORT_TAGS{'all'} = [ @EXPORT_OK ];
local $x = 0;
{
- reap sub { print $x } => 0;
+ reap sub { print $x } => HERE;
local $x = 1;
...
}
...
{
local $x = 1;
- reap sub { $x = 2 } => 0;
+ reap sub { $x = 2 } => HERE;
...
}
# $x is 0
L</reap>, L</localize> and L</localize_elem> effects can't cross C<BEGIN> blocks, hence calling those functions in C<import> is deemed to be useless.
This is an hopeless case because C<BEGIN> blocks are executed once while localizing constructs should do their job at each run.
+Some rare oddities may still happen when running inside the debugger.
+It may help to use a perl higher than 5.8.9 or 5.10.0, as they contain some context fixes.
+
=head1 DEPENDENCIES
L<XSLoader> (standard since perl 5.006).
Inspired by Ricardo Signes.
+Thanks to Shawn M. Moore for motivation.
+
=head1 COPYRIGHT & LICENSE
Copyright 2008-2009 Vincent Pit, all rights reserved.
projects / perl / modules / Scope-Upper.git / blobdiff